1. Field of the Invention
The present invention relates to a process for recovery of low sodium salt from bittern in a cost-effective manner. Low sodium salt is primarily a mixture of sodium chloride and potassium chloride and is useful for those persons who have been advised to eat less common salt because of medical conditions like hypertension.
2. Description of the Related Art
It is known that potassium salt—a mineral found in many fruits, vegetables and legumes such as dried peas and beans—may protect against high blood pressure. Presence of potassium in low sodium salt inhibits sodium-induced hypertension. Reference may be made to “The Heinz Handbook of Nutrition” by Benjamin T. Burton, published for H. J. Heinz Co., by McGraw Hill Book Co. Second Edition, page 132-133, wherein it is mentioned that the dietary need for potassium roughly equals that of sodium. It is also stated that muscular weakness, increased nervousness and irritability, mental disorientation and cardiac irregularities manifest potassium deficiency. Many people, especially in poorer countries, do not have access to sufficient amounts of fresh fruits and vegetables with the result that their dietary needs of potassium have to be met by alternative means.
Since salt is being taken by people almost daily and it is consumed only in very limited quantity, it is an excellent carrier for micronutrients, an important example being iodised salt. Likewise, salt can be enriched with potassium chloride to provide the essential dietary needs. As a result, low sodium salt is gaining popularity although in most cases potassium content in the salt tends to be low. This is partly because of high cost of food grade potassium chloride, increases total cost of the product (see Table 1) thereby making it unaffordable to many.
Reference may be made to Alves de Lima et al. in patent no. BR 9806380 A, 12 Sep. 2000, entitled “Production of dietetic salt by mixing”, wherein it is stated that low sodium dietetic salt is produced by mixing sea salt with potassium chloride, potassium iodate and sodium aluminium silicate, thereby mixing 4 parts of sodium chloride with 6 parts of potassium chloride. The drawback of this process is that one has to separately procure sodium chloride and potassium chloride and blend them together so as to make a solid mixture and also it is difficult to prepare a truly solid homogeneous mixture.
Reference may also be made to Shuqing Wang in patent no. CN 1271541 A, 1 Nov., 2000, entitled “Multi-element low-sodium nutritive salt”, who disclosed the preparation of low sodium nutritive salt by crystallizing salt from saturated brine under vacuum. The salt is then mixed uniformly with salts like KCl and MgSO4.7H2O, followed by mixing with KIO3 and Na2SeO3 solutions, drying and finally mixing with active Ca and Zn lactate. The drawback of this process is that apart from the difficulty of mixing various constituents in a homogeneous solid mixture, salt is to be crystallized from hot saturated brine involving high energy consumption thereby increasing the cost of production.
3. Objects of the Invention
The main object of the present invention is to provide a process for recovery of low sodium salt from bittern, which obviates the drawbacks as detailed above.
Another object of the present invention is to undertake such recovery through intermediate formation of crude carnallite which is a mixture of NaCl and the double salt [KCl.MgCl2.6H2O] of KCl and MgCl2. Crude carnallite can be obtained from low sulphate-containing bittern which may, in turn, be produced from naturally occurring brines of low sulphate content or can be obtained even from high sulphate-containing bitterns such as that obtained from sea brine or sub-soil brine through the desulphatation process described in the pending PCT patent Application No. PCT/IN01/00185 dated 22 Oct., 2001.
Yet another object of the present invention is to vary the composition of crude carnallite in solar pans such that NaCl and KCl in the final composition can be varied as per requirement.
Yet another object of the present invention is to show that valuable nutrients like calcium and magnesium can be introduced into the salt directly from bittern and there is no need of external addition of these nutrients.
Yet another object of the present invention is to prepare low sodium salt under ambient conditions of processing except the final drying of product in an oven.
Yet another object of the present invention is to treat low sodium salt with suitable additives to impart free flowing properties to the salt and for iodisation of the salt by known methods.